Cutting forces in gear hobbing

An accurate kinematic model of the gear hobbing process has been developed in order to compute the gear tooth profile, generated by successive cuts by the hob teeth, as they come into contact with the gear blank. The instantaneous chip cross-section thickness has also been determined at each point on each active cutting edge and from this it has been possible to predict the cutting forces experienced during the machining process. Actual cutting forces were measured using a three-axis force dynamometer mounted directly on the rotating worktable of a prototype CNC gear bobbing machine. The measured forces were acquired by a real-time data acquisition system, and then transformed to the actual tool/work-piece interface. The paper presents a brief description of the theoretical cutting force model and a comparison between the model and experimental test results. Good correlation was achieved, and serves to illustrate the complicated cyclic nature of the cutting force behaviour during the gear bobbing process.